$81 B

Age:

58

America's richest man, Bill Gates, is using his billions to effect major social change around the globe. The Bill & Melinda Gates Foundation has given away $30 billion since 2000, a fortune that on its own would be the 16th largest in America. Smallpox has disappeared, polio is nearly gone too, and the American education system has gotten an overhaul. Gates is not the only one responsible for the changes, but none of them would have happened without the help of the biggest philanthropist in world history. Now he's taking on the deadliest animal on Earth, the mosquito. Malaria cases are down 25% since 2000, but there are still 200 million cases worldwide, and Gates is throwing billions toward making that number zero. He's also taking sight at second deadliest animal on Earth, humans. Along with Microsoft cofounder Paul Allen, Gates is funding a Washington state-based group fighting for universal background checks on guns. Meanwhile, Gates keeps getting richer, adding $9 billion to his net worth in the last year. The gain is partly due to a sharp rise in shares at Microsoft, where Gates stepped down as chairman to take a different role advising current management on new products and technologies. His fortune is also up thanks to big returns on his investments in Canadian National Railway and trash company Republic Services, which Gates holds through his investment firm Cascade. He also owns chunks of tractor maker Deere & Co. and South American McDonald's franchise Arcos Dorados ("golden arches" in Spanish). [...] more